USPTO Patents Application 10052038

WATERBORNE COATINGS

Field of the Invention

5 This invention is in the area of waterborne coatings, in particular, waterborne coatings to

be applied to surface coverings such as floor coverings.

Background of the Invention

Resilient surface coverings, in particular, floor coverings, are widely used. Although they
) are constructed to have varying degrees of flexibility, they are "resilient" when compared to
3 conventional natural materials, such as ceramic tile.

Chemical embossing has been used to create surface coverings with a desired three-
dimensional appearance. Chemical embossing typically involves applying a foamable layer to a
substrate, where a foaming agent, inhibitor and/or promoter is applied in a pattern. The foamable
1=5 layer is subjected to conditions that cause foaming only to occur in selected regions, which
regions are in register with the pattern.

Many surface coverings include a wear layer in addition to the chemically embossed
J foam layer. The wear layer can also include a top coat. The prior art generally teaches

chemically embossing a foamable layer, applying a wear layer, and then curing the wear layer.
From a processing standpoint, it would be advantageous to be able to cure the wear layer while
the foamable layer is being cured. However, a limitation associated with curing the foamable
layer and the wear layer at the same time is that if the wear layer is too rigid, the chemical
embossing is restricted. If the wear layer is too flexible, the stain resistance and wear properties
such as scratch resistance of the wear layer are reduced.

From an environmental standpoint, it is desirable to apply coating compositions to
substrates using either one hundred percent solids coating compositions or waterborne coating
compositions, to minimize the use of organic solvents. The one hundred percent solids coating
compositions typically include photocurable resins, such as acrylates. These are not typically
cured with heat, but rather, by irradiation.

A148 1599.1
RTP35175vl

Accordingly, it would be desirable from both a processing and an environmental
standpoint to have waterborne coating compositions that cure with heat in conjunction with
foamable layers that expand and cure with heat. It would also be desirable to have waterborne
coating compositions that are rigid enough to provide suitable stain resistance and wear
5 resistance, but that are flexible enough that a foamable layer can be chemically embossed while
the coating layer is cured. The present invention provides such a waterborne coating
composition.

Summary of the Invention

1Q Waterborne coating compositions, methods of applying such compositions, and substrates

O coated with such compositions are described. The compositions include an aqueous dispersion
yi. of a polyurethane resin, an epoxy resin, and a polyvinyl chloride resin. In one embodiment, one
y or more of these resins includes reactive functional groups that react with epoxy groups and/or
W aminoplasts. The compositions can also include an aminoplast such as a melamine, and one or
15 more curing agents. Additionally, the compositions can include flatting agents, colored metallic
ll and/or polymeric particles, surfactants, rheology modifiers, defbamers, coalescing aids and hard
particles.

O In one embodiment, the composition is an aqueous dispersion that includes an epoxy

dispersion (0.01-30 % by weight, in another embodiment, 14-30% by weight), polyurethane

20 dispersion (0.01-35 % by weight) and a vinyl dispersion (4-60 % by weight, in another embodiment,
4-40% by weight). The composition also includes a melamine crosslinker (3.5-9. 1 % by weight). In
another embodiment, then composition further includes two curing agents, one that induces curing at
a faster rate and/or a lower temperature than the other. Examples of such curing agents are Nacure
2547, which can, for example, be present at between 0.64 and 2% by weight, and Nacure 1557,

25 which can, for example, be present at between 0.01 and 2.9% by weight.

The coating composition can be applied to virtually any surface and cured using
conventional heat curing techniques, whether or not there is a chemically embossed or
embossable layer. However, it is advantageously used in surface coverings in combination with
a chemically embossed or embossable layer. For example, the coating composition can be

30 applied directly to a felt backing layer, a polymeric support layer or a similar substrate and cured.

A148 1599.1
RTP35175vl

2

The felt backing, polymeric support layer or similar substrate can include, for example, a hot
melt calendared layer, a foamable gel layer and/or a clear wear layer. A pattern including a
foaming agent, promotor or inhibitor can be printed or applied adjacent to the foamable gel such
that, when heated, a chemically embossed surface is produced in register with the agent,
5 promotor or inhibitor. The waterborne coating layer is typically the top coat, although it need not
be the top coat

Optionally, one or more of the above-layers can be mechanically embossed. This is
typically accomplished by heating the layer to be embossed to a temperature at which the layer is
softened and subjecting the softened layer to an embossing roll under pressure.
10 In one embodiment, the surface covering includes a chemically embossed layer and a

O cured top coat, which are both cured in a single heating step or plurality of heating steps. Ideally,
f£ the top coat has good wear and stain resistance properties, and the chemical embossing in the
W foamable layer occurs while the cop coat is cured. However, in other embodiments, the coating
£i j composition can be applied to a surface covering that does not include a chemically embossed
layer.

M Detailed Description of the Invention

££ The present invention is directed to waterborne coating compositions, methods of

n j applying such compositions, and substrates coated with such compositions. The compositions
20 include an aqueous dispersion of a polyurethane resin, a epoxy resin, and a polyvinyl chloride

resin. The compositions also can include a melamine and a curing agent, and optionally include

more than one curing agent.

The compositions described herein including a combination of PVC, polyurethane and

epoxy resins provide a better chemical embossing capability when compared to coatings
25 prepared from compositions including only polyurethane and epoxy resins. The chemical

embossing is sharper and deeper, and the same (or better) wear performance is attained.
The coating composition can be applied to virtually any surface and cured using

conventional heat curing techniques, whether or not there is a chemically embossed surface.

However, it is advantageously used in surface coverings in combination with a chemically

A148 1599.1
RTP35175vl

3

embossed layer. The thickness of the coating layer is typically between 0.2 and 1 mils, although
thicknesses outside of this range can be prepared.

Composition

5 The composition is an aqueous dispersion that includes three types of dispersed particles -

polyurethane, polyvinyl chloride and epoxy resins. Any suitable particle size that can be
stabilized in a dispersion can be used. In one embodiment, the composition also includes a
melamine resin. In another embodiment, the composition includes one or more curing agents.
When two or more curing agents are used, they can effect the cure at different temperatures or

1 0 different times at the same temperature.

jrji Polyurethane Resin

W Any suitable polyurethane resin can be used. In one embodiment, the polyurethane resins

yj include reactive groups other than epoxy groups, such as hydroxy and/or thiol groups, that react

Ip with the epoxy groups in the presence of an acidic catalyst at elevated temperatures. In one

F embodiment, the epoxy resins have particle sizes are in the range of between 5 and 300 nm, and

M ! representative molecular weights in the range of 1 ,500 and 1 50,000. Examples of suitable

O polyurethanes include SpencerKellogg Products EA6010 (30% solids), and various Daotan

m polyurethanes (Solutia), Bayhydrol polyurethane dispersions (Bayer), such as Bayhydrol PR 435,

20 can also be used. Bayhydrol PR 435 is an aqueous aliphatic polyurethane dispersion that
contains only 5% by weight of organic cosolvent, and includes about 35 wt. % solids.

Polyvinyl Chloride Resin
As used herein, polyvinyl chloride is intended to include homopolymers including only
25 vinyl chloride units, copolymers that include two homopolymers such as vinyl chloride and vinyl
acetate, and compositions including such homopolymers and copolymers. Any suitable
polyvinyl chloride resin can be used.

In one embodiment, the polyvinyl chloride resins include reactive groups other than
epoxy groups, such as hydroxy and/or thiol groups, that react with the epoxy groups in the
30 presence of an acidic catalyst at elevated temperatures. In one embodiment, the resins are

A148 1599.1
RTP 35175vl

4

hydroxy terminated resins. In one embodiment, the polyvinyl chloride resins have particle sizes
are in the range of between 40 and 600 nm, and representative molecular weights in the range of
5,000 and 60,000. One example of a suitable resin is UCAR Waterborne Vinyl AW-845 (Union
Carbide), which has an emulsion particle size of about 0.08 micron, a molecular weight of about
5 24,000, a glass transition temperature of about 80°C and a hydroxy (OH) equivalent weight of
about 1005.

Epoxy Resins

Epoxy resins are well known to those of skill in the art. In one embodiment, the epoxy
10 resins include reactive groups other than epoxy groups, such as hydroxy and/or thiol groups, that
if react with the epoxy groups in the presence of an acidic catalyst at elevated temperatures. The

O epoxy resins may include more reactive groups, for example, more hydroxy groups, than epoxy

in

rj ? ' ' groups. In one embodiment, the epoxy resins have particle sizes are in the range of between 300

H and 1,000 nm, and representative molecular weights in the range of 400 and 8,000. An example

IP of a suitable epoxy resin is EPI-REZ Resin 3541 -WY-50 (Resolution Performance Products).

O This resin includes approximately 5 hydroxy groups and 2 epoxy groups per molecule.

Melamine

o

Td Aminoplasts, of which melamines are an example, can be present in the compositions.

20 Melamines, also known as triaminotriazines, are well known to those of skill in the art. The
melamines may or may not be partially or substantially methylolated, and the methylol groups
may or may not be partially or substantially etherified with C M0 straight chain, branched or
cyclic alkyl groups.

Many of these compounds are commercially available and sold, for example, as Cymel
25 crosslinking agents by the Cytec Industries, Inc., for example Cymel 301, and as Resimene resins
by Solutia. Resimene 745 is an example of a suitable Resimene resin.

Curing Agents

The curing agents are typically acidic catalysts. They can be used to catalyze the curing
30 reaction between the melamine component, polyurethane resins that include reactive groups,

A148 1599.1
RTP35175vl

5

such as hydroxy-urethanes, the epoxy component, and polyvinyl chloride resins that include
reactive groups, such as hydroxy-PVC resins. Examples of suitable catalysts include sulfonic
acids, such as methane sulfonic acid, alkylated arylsulfonic acids such as p-toluenesulfonic acid,
alkylated napthylsulfonic acids such as dinonyl napthalene sulfonic acid and dinonyl napthalene
disulfonic acid. Other acids such as citric acid, maleic acid, phthalic acid and the like can also be
used. The catalysts may be in the free acid form, or can be stabilized, for example, by using an
amine to neutralize the acid, for example, an amine blocked dinonylnaphthalene sulfonic acid
catalyst. The only restriction is that the catalysts are compatible with other components in the
system. Such catalysts are well known to those of skill in the art and their selection is within the
capability of the ordinary artisan.

Nacure catalysts (King Industries) are examples of suitable catalysts. Specific examples
include Nacure 2547 and Nacure 1557. Nacure 2547 is a faster curing catalyst and 1557 is a
slower curing catalyst. Nacure 1557 (dinonylnaphthalene sulfonic acid type) requires about 40°C
higher curing temperature than Nacure 2547 (p-toluene sulfonic acid type. In one embodiment,
when two curing agents that promote curing at different temperatures are used, the curing
temperatures differ by at least about 25°C. When a combination of catalysts is used, the catalysts
may each effect a cure at different temperatures, or at different times at the same temperature.

Surfactants

Surfactants can be added to impart additional stain resistance to the coated substrate.
Examples of suitable surfactants include fluoroaliphatic and non-ionic surfactants. Combinations
of surfactants can also be used. Examples of suitable surfactants include Fluorad surfactants
such as Fluorad FC-340 and Fluorad FC-170-C (3-M Company) and Igepal-type surfactants. In
one embodiment, a non- foaming commercially available surfactant is used, which has the
properties of both a surfactant and defoamer. CoatOSill21 1 (Witco) is an example of a suitable
non-foaming surfactant. It is a composition of trisiloxane alkoxylate, siloxane polyalkyleneoxide
copolymer and polyalkylene oxide.

A148 1599.1
RTP 35175vl

6

Optional Components

Defoamers can be added in suitable quantities. Colloid 640/rhodoline 640 is an example
of a silica-type defoamer that includes petroleum hydrocarbon, hydrophobic silica and
amorphous silica.

5 Various flatting additives are known for adjusting the gloss level of coatings. Such

additives can be added to the compositions described herein. Pergopak M-3 is an example of a
suitable gloss-adjusting additive. Pergopak M3 can be included in various concentrations to
provide varying levels of gloss. For example, a high gloss can be obtained with little or no added
Pergopak M3, a low gloss with about 1.12%, and an ultra-low gloss with about 2.38% by weight.

10 Typically, no more than about 2.5% by weight is used.

q Metallic and/or polymeric particles, hard particles and colored particles can also be

S added. Coalescing aids can also be added. Texanol coalescing aids (Eastman Chemicals) are an
5f example of a suitable coalescing aid. Rheology modifiers, such as Acrysol® brand rheology
U modifiers, can also be added. Acrysol RM-825 is an example of a suitable non-ionic rheology
0 modifier.

p Hard particles include, but are not limited to, aluminum oxide, quartz, carborundum,

I* silica and glass beads. In one embodiment, the hard particles are particles with a hardness of 6 or

p more on the Mohs scale.

?! ii

20 Surface Coverings

Virtually any surface covering substrate can be coated with the coating compositions
described herein. Examples of surface covering substrates that can be prepared using the
compositions and methods described herein include those described, for example, in U.S. Patent
No. 4,781,987, U.S. Patent No. 4,855,165 and U.S. Patent No. 5,643,677, the contents of which
25 are hereby incorporated by reference.

Examples of surface covering substrates include resilient sheet and tile goods that include
crosslinked wear layers, such as those derived from urethanes, (meth)acrylated urethanes,
unsaturated polyesters and the like, all of which are well known to those of skill in the art.

The surface covering substrates may include a resilient support surface. Such surfaces
30 are well known in the art, and include, for example, vinyl polymers such as polyvinyl chloride.

A148 1599.1
RTP35175vl

7

The layers can be formed, for example, from backing materials, plastisols, foamed plastisols,
randomly dispersed vinyl particles, stencil disposed vinyl particles, and the like. The selection of
these materials is within the skill of an ordinary artisan. The thickness of such support surfaces
are typically, but not necessarily, in the range of 10 to 100 mils. A felt base layer may also be
used. The thickness of such a felt layer is typically, but not necessarily, in the range of 15 to 30
mils.

The resilient support layer can include or be adjacent to a hot-melt calendared layer, for
example, of a polyvinyl chloride, polyolefin or other thermoplastic polymer. The thickness of
this layer may be from 15 to 60 mils, although thicknesses outside this range can be used.

In one embodiment, the surface covering includes a chemically embossed layer, formed
before, during or after the coating composition is applied and cured. This type of layer is
typically applied as a foamable gel, and the gel can include foaming agents or foaming promoters
or inhibitors. The thickness of the gel layer is typically, but not necessarily, in the range of 6 to
20 mils in an un-blown state, and between 12 and 60 mils when blown ("cured"). The foaming
agents, promoters or inhibitors can be present in the gel layer and/or present in a printed pattern
in an adjacent layer to the gel layer. Printed pattern layers are typically less than one mil in
thickness when applied using a rotogravure process, or one mil or greater when applied using a
screen process. Such agents provide chemical embossing in register with the agents, where the
foamed portion corresponds to the presence of the foaming agent and/or promotor, and the un-
foamed portion corresponds to the absence of the foaming agent and/or the presence of a foaming
inhibitor. Typically, the foaming is done by subjecting the foamable layer to elevated
temperatures, for example, in the range of 120 to 250°C, in one embodiment, between 180 and
250°C, for between 0.5 and 10 minutes, and these conditions can also be used to cure a top layer
including the compositions described herein.

A clear wear layer can be but is not necessarily applied over the gel layer, typically but
not necessarily with a thickness of between 10 and 20 mils. Such layers are commonly formed
of a material that includes a PVC plastisol.

The top coat layer formed using the waterborne coating compositions described herein,
can be, but is not necessarily in the range of between 0.2 and 5 mils thickness.

A148 1599.1
RTP35175vl

In some embodiments, one or more layers can be mechanically embossed. In those
embodiments where the cured top coat layer is mechanically embossed, the embossing may take
place after the top coat layer is cured and then heated to soften the layer.

In one embodiment, the finished surface covering includes a resilient support surface, a
5 chemically embossed layer and a top coat layer. In this embodiment, a foamable layer can be
applied to a support layer, a print layer or other layer, where the foamable layer includes or is in
contact with foaming agents, inhibitors and or promoters, either throughout the entire layer or in
the form of a pattern. The top coat layer is formed by applying the waterborne coating
composition to the foamable layer or a layer directly or indirectly overlying the foam layer, and
10.. curing the composition. For example, a clear wear layer may be applied to the foamable gel

P layer, and the coating composition applied over the clear wear layer.

O

yl In one embodiment, the waterborne composition is cured in the same relevant time frame

Ti\

^ as the foamable layer. In those embodiments where the foamable layer includes a pattern of

~; foaming agents, inhibitors and /or promoters such as to form a chemically embossed layer when

\S the foamable layer is "cured" or foamed, the waterborne coating does not significantly adversely

affect the chemical embossing of the foamable layer. The wear layer has the ability, when

ri thermally cured, to conform to the physical deformations in the cured foamable layer and has

C3 improved scratch and stain resistance properties relative to the properties of the foamable layer.

20 Methods of Applying the Composition

The coating composition is advantageously stirred to maintain the dispersion of the
particles until it is to be applied. The coating composition can be applied to virtually any surface
using techniques well known to those of skill in the art, for example, roll coaters, flow coaters or
blade applicators such as bird blades and drawdown blades. After the compositions are applied,
25 they can be heated, for example, above around 100°C, to remove the majority of the water that is
present.

Chemical Embossing

In those embodiments in which there is a foamable gel layer, the layer may include
30 various foaming agents, foaming inhibitors and/or foaming promoters. Such agents, inhibitors

A148 1599.1
RTP 35175vl

9

and/or promoters, which are well known to those of skill in the art, can also be present in an
adjacent print layer. With different amounts or concentrations of foaming agent in a particular
region, for example, in register with a print pattern, the foamable layer is foamed to different
levels, resulting in chemical embossing. The presence of a foaming promoter or inhibitor in the
5 pattern also affects the degree of foaming in the pattern.

Mechanical Embossing

Mechanical embossing is typically done by subjecting the surface covering to an
embossing roll under pressure, typically at a temperature at which the layer to be mechanically
ip s embossed is softened enough to be embossed. After the mechanical embossing, the layers may
13 be annealed at a lower temperature, if desired. Such techniques are well known to those of skill

m in the art.

rjj '

::

W Methods of Curing the Composition

03

IS The compositions can be cured using conventional heat curing techniques, for example,

J3?5j

U exposure to microwave, IR irradiation or heated air impingement ovens, whether or not there is a

r " chemically embossed surface. However, it is advantageously used in surface coverings in

0 combination with a chemically embossed layer.

r 2 : 2 .

1 .

Suitable temperature ranges for heat curing a foamable layer and a waterborne
20 composition including epoxy resins and/or melamine resins are well known to those of skill in
the art. Temperatures typically range from 120 to 250°C, in one embodiment, from 180 to
250°C, although temperatures outside of these ranges can be used provided they are effective at
curing the foamable layer and/or waterborne coating composition. The heat curing can be
effected at a plurality of temperatures and heating stations. Alternatively, the curing can be
25 effected at one temperature, where one of the foamable layer and the wear layer is cured faster
than the other. For example, when a combination of curing agents is used, one curing agent in
the composition can initiate and partially cure the top coat at a first temperature while the
foamable layer is expanding and curing, and a second curing agent can finish the cure of the top
coat at a second, higher temperature. This can permit the chemical embossing to take place
30 while the top coat is flexible, and permit the top coat to completely cure after the chemical

A148 1599.1
RTP35175vl

10

embossing takes place. This advantageously provides adequate chemical embossing and a rigid
top coat.

An example of a suitable surface covering includes a hot-melt calendared layer overlying
a felt support layer and a foamable gel layer overlying the hot-melt calendared layer. A print
5 layer overlies the foamable gel layer, and a clear wear layer overlies the print layer. The
waterborne coating is used to form a top coat layer that overlies the clear wear layer.

The present invention will be better understood with reference to the following non-
limiting example.

1(X Example 1 : Example of a waterborne composition

y In one embodiment, the epoxy dispersion is 0.01-30%, the polyurethane dispersion is

|H. " 0.01-35%, the vinyl dispersion is 4%-60%, Nacure 2547 is 0.64%-2%, Nacure 1557 is 0.01%-

fU

q 2.9%, and a melamine crosslinker such as Resimene 745 is 3.5%-9.1% by weight of the

J2 composition. Resin solids level are 50%, 35% and 39%, respectively, for epoxy dispersion,

16 polyurethane dispersion and vinyl dispersion resins. In another embodiment, the epoxy

M, dispersion is 14-30% by weight, and the vinyl resin is 4-40% by weight of the composition. In

1 3 another embodiment, the epoxy resin and polyurethane dispersion are each present in at least one

O percent by weight of the composition.

20 Example 2: Flooring Structure Including the Waterborne Coating Composition

A flooring structure including a 15 mils felt backing layer, a 20 mils PVC melt-
calendared layer, a 10 mils foamable gel layer, a rotogravure printed pattern with inhibitor
containing inks in specific locations, and a 15 mils gelled clear plastisol layer was prepared. A

25 top coat coposition including 306.00 gram Bayhydrol PR 435, 259.10 gram EPI-REZ Resin
3541-WY-50, 69.60 gram UCAR Waterborne Vinyl AW-875, 90.25 gram Resimene 745, 5.0
gram CoatOSil 121 1, 17.90 gram Texanol, 3.90 gram Acrysol RM-825, 7.60 gram Nacure 2547,
9.40 gram Nacure 1557 and 23 1 .25 D.I. water was prepared. The composition was applied to the
plastisol layer by forward roll coater at an application rate that resulted in about 0.5 mils dry

30 coating thickness. The coated substrate was conveyed into a fusion and expansion oven heated at

A148 1599.1
RTP 35175vl

11

190°C for two minutes. The final expanded and cured composition exhibited excellent chemical
embossing and excellent top coat stain resistance.

The present invention is not restricted solely to the descriptions and illustrations provided
above, but encompasses all modifications envisioned by the following claims.

A148 1599.1
RTP35175vl